Fast stereo rendering

This makes a lot of sense in OpenGL (with a Geometry Shader) but in something like Metal I'm not sure you would get a lot of efficiency gains due to the way the command encoder manages state where each encoder would be a separate target with set of render states. With Vulkan you can actually re-use command buffers so theoretically you could get even better performance.

As far as the additional memory cost; the 2x memory on a PS4 may seem trivial but it certainly is not on a mobile device trying to do VR.

Great article, though. Inigo is truly a genius (his articles on tracing equations is a regular reference whenever I do any analytic gpu stuff).

Nice write up. Both Unreal Engine (http://docs.unrealengine.com/latest/INT/Support/Builds/Relea...) and Unity3D have added support for this recently.

This is quite logical and I've been wondering--isn't this at odds with (future) dual SLI one-eye-per-card techniques?

Would it make sense for dual SLI VR setups to go back to the old "card 1 renders the top half of the screen and card 2 goes bottom"? Then you wouldn't need 2x sized framebuffers.